Flexible bulk containers made from woven polypropylene, having a coating of thermoplastic polypropylene containing a polyol ester of a monocarboxylic acid anti-static agent are disclosed in Pappas U.S. Pat. No. 5,071,699. Optionally the bulk containers of Pappas may have conductive fibers interwoven with the woven polypropylene. The conductive fibers may be metal such as stainless steel or copper, or a carbon fiber. Preferably the conductive fiber is itself a plastic material such as nylon or polyester monofilament which has been coated with a highly conductive metal such as silver or copper.
Flexible bulk containers containing electrically conductive polyolefin threads are also disclosed in U.S. Pat. No. 5,092,683 to Wurr. In this patent the electrically conductive polyolefin threads contain dispersed carbon black and/or graphite and are woven into both the warp and weft of the fabric. Sheath-core filaments having conductive cores are known and are disclosed in U.S. Pat. No. 5,202,185 to Samuelson and U.S. Pat. No. 3,803,453 to Hull. The cross-section of the core of the Samuelson filaments is multilobal, while cross-section of the core of the Hull filaments is circular. In Samuelson the sheath is either nylon or polyester and the core is polyethylene containing conductive carbon black.
It is an object of the present invention to provide a fabric and a container having anti-static properties in which the filaments are sheath-core filaments in which the core is conductive and the sheath is nylon or polyester, and the filaments having the conductive core are combine in the fabric as part of a nylon or polyester carrier yarn that is woven into the fabric at spaced intervals. The nylon or polyester of the sheath protects the conductive core, and the non-sheath-core nylon or polyester filaments in the carrier yarn have many of the same physical characteristics as the sheath-core fibers.